Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines generally comprise a rotor with a rotor hub and a plurality of blades. The rotor hub is set into rotation under the influence of the wind on the blades. The rotation of the rotor shaft drives the generator rotor either directly (“directly driven”) or through the use of a gearbox.
In most conventional wind turbines, the rotor hub is mounted on one end of the rotor shaft. The rotor shaft is rotatably mounted in a support structure inside the nacelle and the nacelle is rotatably mounted on top of a wind turbine tower.
The hub and nacelle may comprise complex mechanical and electrical equipment that can produce heat during operation e.g. pitch motor and generator respectively. It is generally desirable to avoid heating up of these components.
Also, especially during winter, it may happen that components of a wind turbine (e.g. components using lubricants) may need to be heated up before starting if the wind turbine has been motionless for some time due to e.g. maintenance. In these cases, heaters may be used.
Reliable operation of various components housed inside the hub and/or the nacelle may require certain specific temperature and/or humidity ranges. In order to keep temperatures at desired ranges, special ventilators, fans, or other air conditioning systems may typically be provided inside the nacelle.
This is of special importance in offshore wind farms for which outside conditions may be extreme.
Document WO0159296 discloses a direct drive wind turbine comprising a hub with a plurality of blades, the hub being rotatably mounted relative to an axle part.
Document ES2163362 describes a wind turbine tower with a frame comprising a portion extending forward into the hub. The rotor hub with its plurality of blades is rotatably mounted upon said portion of the frame. The rotor hub is coupled to a rotor shaft arranged within said frame.
In these kinds of configurations, the hub and the nacelle are substantially separate, closed spaces. In these configurations, in order to guarantee proper air conditioning of the hub, (which may involve heating, cooling, pressure and/or humidity control), additional air treatment devices such as fans, filters, air dampers, or dehumidifiers may typically be provided inside the hub. However, this is an expensive solution and may be complicated as this kind of equipment takes up room in an inherently compact space such as e.g. the rotor hub.